Gauge cylinder assembly for position indicator and indicator system including such cylinder

ABSTRACT

A volumetric gauge cylinder for a position indicator comprising a closed cylinder having connections for pressure fluid at its ends. A non-rotatable axially movable piston is capable of movement within the cylinder under the fluid pressure, and a rotatable spindle extends along the length of the cylinder and has a helical external configuration cooperating with, and forming a sealed fit with a correspondingly shaped opening in the piston so that linear movement of the piston is translated into rotary movement of the spindle. The spindle is operationally connected to an external indicator which is caused to rotate in accordance with movement of the spindle.

I United States Patent 1151 3,654,891 Aas et al. 1451 Apr. 11, 1972 54]GAUGE CYLINDER ASSEMBLY FOR 1,633,322 6/1927 Gregory ..73/320 POSITIONINDICATOR AND 1,643,753 6/1927 Slattery.... ..91/1 x INDICATOR SYSTEMINCLUDING 2,574,262 11/1951 Heck 137/139 SUCH CYLINDER 3,156,255 1l/l964Gasquet et al ..25l/289 3,191,621 6/1965 McKinnon et a1. ....251/289 X[72] Inventors: S jorn Ans, Tyn m Eng n K 3,439,706 4/1969 Barrett..137/554 Brathen, R ukan, Norway 731 Assignees Norsk Hydro VerkstederA/S, Rjukan, 'w CaPOZi Norway 7 Attorney-Wenderoth, Lind & Ponack [22]Filed: DEL 29,1969 57 ABSTRACT [2]] Appl' 8883 A volumetric gaugecylinder for a position indicator comprising a closed cylinder havingconnections for pressure fluid at [30] Foreign Application Priority Dataits ends. A non-rotatable axially movable piston is capable of movementwithin the cylinder under the fluid pressure, and a Dec. 30, 1968 Norway..5235/68 rotatable Spindle extends along the length of the cylinder and[52] U S Cl 116/124 73/320 73/419 has a helical external configurationcooperating with, and 6/1 18 /5 53 251/289 forming a sealed fit with acorrespondingly shaped opening in [51] Int. Cl. "(309i 9/00 the Pistonso that linear movement of the Piston is translated [58] Field of Search16/1 18, 125; 73/389, 320, into rotary movement of the spindle Thespindle is p 73/419; 137/307, 139, 319, 553, 344; 251/289; 91/1 tionallyconnected to an external indicator which is caused to rotate inaccordance with movement of the spindle. f t d [5 6] Re e 1 Claims, 4Drawing Figures UNITED STATES PATENTS 899,029 9/ 1908 Connet 137/553PATENTEDAPR 11 1972 SHEET 2 [IF 2 Saab J 0m HM rm #22 re Eratfizn,

GAUGE CYLINDER ASSEMBLY FOR POSITION INDICATOR AND INDICATOR SYSTEMINCLUDING SUCH CYLINDER This invention relates to position indicatingsystems of the kind including a volumetric gauge cylinder and isparticularly concerned with the construction of a gauge cylinder used insuch systems. Indicator systems of this kind are used in conjunctionwith hydraulic operating systems so as to provide an indication of theposition of a movable mechanical element which is actuated by thehydraulic fluid of the system. Such systems are particularly suitablefor use in indicating the position of remotely controlled hydraulicallyoperated valves such as butterfly valves.

The gauge cylinder of such a system has a piston which is operated bythe hydraulic fluid controlling the mechanical element and the positionof this piston is thus used as an indication of the position of theelement. For this purpose the piston is normally provided with a pistonrod which extends out of the end of the cylinder so as to actuate anindicator device such as a pointer working over a scale. Owing to therisk of leakage of the hydraulic fluid along the piston rod at the pointwhere the rod leaves the housing cylinder the cylinders need to be veryrobustly constructed and it is desirable to provide a construction inwhich the components can be made more simply and more cheaply.

According to the present invention a gauge cylinder of this same generaltype comprises a closed cylinder having connections for pressure fluidat its end, a non-rotatable piston which is capable of movement withinthe cylinder under the fluid pressure, a rotatable spindle extendingalong the length of the cylinder and having a helical externalconfiguration cooperating with, and forming a sealed fit with acorrespondingly shaped opening in the piston so that the linear movementof the piston is translated into rotary movement of the spindle and anexternal indicator which is caused to rotate in accordance with movementof the spindle. Since there is no need for a piston rod extendingoutside the cylinder itself the construction as a whole can be muchsimpler and cheaper. The external indicator may be driven by means of anextension of the spindle which is of reduced diameter and this presentsmuch less difficulty in obtaining an effective seal. Alternatively theindicator can be driven by way of a magnetic coupling of which one partis connected to the indicator. The end of the cylinder then needs to beformed of non-magnetic material and under these circumstances no seal atall is required.

The spindle is preferably of rectangular cross-section but other shapesare also possible provided that the necessary helical configuration isachieved. This configuration is conveniently obtained in the case of ametal bar of rectangular cross-section merely by twisting. The spindlemay be journaled at one end in one end of the cylinder and the other endmay be supported so as to be capable of slight transverse movement. Thisprevents jamming of the piston if there is any small distortion ofspindle since it enables the spindle to yield laterally as the pistonmoves.

Constructions in accordance with the invention will now be described byway of example with reference to the accompanying drawings in which:

FIG. 1 is an axial section along the line CC in FIG. 3 through a gaugecylinder, and also including a schematic view to a smaller scale of theremainder of the hydraulic system,

FIG. 2 is an axial section along the line 8-3 in FIG. 3,

F IG. 3 is a transverse section along the line A-A in FIG. 2, and

FIG. 4 is a sectional view similar to the top portion of FIG. 2 of amodified form of construction.

Turning first to FIG. 1 the gauge cylinder is shown as 1 and isconnected in series with a double acting hydraulic cylinder 4 and avalve 6 operated by this cylinder. Since the hydraulic cylinder itselfis of a known type it is shown to a reduced scale but in practice itwill have exactly the same volume as the gauge cylinder.

The gauge cylinder 1 encloses a piston 3 having sealing rings 7 engagingthe cylinder wall and formed with apertures containing two spring biasedrelief valves 8 and 10. These valves are of the ball type having balls12 biased by means of helical springs 14 so as to permit fluid flow inone direction or the other when the pressure across the piston exceeds apredetermined value.

The piston 3 cooperates with a spindle 2 formed from a bar ofrectangular cross section which has been twisted to form a helix with anangle about 360 between the ends of the spindle. The spindle 2 passesthrough a corresponding opening in the piston 3 with which it forms asealing fit so as to prevent fluid passing from one side to the other ofthe piston. For this purpose a guide plate 16 attached to the piston bymeans of a screw 17 is formed with an aperture corresponding to thecross-sectional shape of the spindle and also retains a sealing member18 which encircles the spindle 2.

At its upper end as seen in FIGS. 1 and 2 the spindle 2 is formed withan axial extension constituted by a relatively thin stem 22 extendingthrough the end 38 of the cylinder via a combined thrust bearing andpacking 24. On the outside of the cylinder the stem 22 is connected toan indicator for example, in the form of a pointer cooperating with ascale (not shown) so as to indicate the angular position of the spindle2 and hence the axial position of the piston 3. The other end of thespindle 2 is supported in a recess 27 which has a somewhat largerdiameter than the spindle so that the latter is capable of slighttransverse movement. This permits the end 25 of the spindle 2 to walk inthe recess 27 to allow for any slight distortions of the spindle 2.

The cylinder 1 also encloses a hollow guide rod 26 which extends throughan aperture in the piston 3 defined by bushing 28 provided with apacking. The opposite ends of the rod 26 are seated in the ends 36 and38 of the cylinder 1 and the hollow interior shown as 30 communicates atthe lower end with a port 32 for pressure fluid. At the other end anopening 40 forms a port from the passage 30 communicating with a recess37 in the cylinder end 38. The rod 26 serves both as guide for thepiston 3 which prevents rotation of the piston and also a fluidconnection for the pressure fluid between the inlet 32 and the oppositeend of the cylinder 1. In this way both the connection 32 and a secondconnection 42 for the pressure fluid may be located at the same end ofthe cylinder 1 thus facilitating the construction and the mounting ofthe cylinder.

The connection 32 leads to a pipe 44 connected at one end of thecylinder 4 which has a piston 56 and a double piston rod 57. The piston56 is connected to the valve or other mechanical element of which theposition is to be indicated. The other end of the cylinder 4 isconnected by way of a pipe 48 to a control valve 50 which in its turn isconnected to a source of pressure fluid by pipes 58 and 59. From thisvalve a further pipe 52 extends to the second connection point 42 of thecylinder 1. The control valve 6 is a manually operated fourway valvehaving three positions.

The operation of the system is as follows. Axial movement of the piston3 within the cylinder 1 under the control of fluid pressure in eitherdirection produces a rotary motion on the spindle 2 since the piston 3is prevented from rotating by the rod 26. In the position shown in FIG.1 pressure fluid from the valve 6 has moved the piston 56 of thecylinder 4 to the righthand end of this cylinder. The pressure fluidwhich was previously located at the right-hand side of the piston 56 hasbeen forced along the pipe 44 through the connection 32 and thencethrough the passage 30 and out through the port 40 into the upper partof the cylinder 1. This has forced the piston 3 downwardly to its lowestposition as shown in FIG. 1 thus resulting in a corresponding turningmovement of the spindle 2.

Owing to the fact that the volumes of the cylinders 1 and 4 are the samemovements of the piston 56 from one end to the other of its cylinder 4will result in synchronous movements of the piston 3 from one end to theother of its cylinder 1 with corresponding movement of the pointer 20 sothat the latter will at any time indicate the position of the piston 56and hence the position of the valve or other mechanical elementcontrolled by the piston rod 57.

When the control valve 6 is moved so as to reverse the direction of flowmovement will take place in the opposite direction to that justdescribed. The pressure fluid will then flow directly into the cylinder1 through the pipes 59 and 52 and lift the piston 3 to its opposite endposition and at the same time the pressure fluid on the upper side ofthe piston 3 will be forced out through the tube 44 so as to move thepiston 56 of the working cylinder 4 to its other extreme position.During this movement the pointer 20 will indicate the position of thepiston 57 at any time. If it is desired to lock the piston 57 in anintermediate position the control valve 6 is placed in an intermediateposition in which both pipes 48 and 52 will be closed. This prevents theflow of pressure medium and both pistons will be locked in correspondingpositions in the respective'cylinders.

The system is designed so that if a minor leakage should occur, forinstance a leakage of pressure fluid from one side to the other of oneof the pistons, both pistons may nevertheless be moved to the respectiveend positions so that the system is self-adjusting. This is accomplishedby the provision of the I reflief valves 8 and 10 in the piston 3. If,for example, the

piston 56 has not reached one of its end positions although theindicator shows this position and the piston 3 has reached the endposition, further movement of the piston 56 will lead to an increase inthe pressure on the operating side of the piston 3. Since this pistoncannot move any further the result will be that one relief valve will beopened and will remain open until sufficient pressure fluid has flowedthrough the valve to enable the piston 56 to reach its end position. Inother words this movement of the piston 56 will not be accompanied bycorresponding movement of the spindle 2 and pointer and the error willthus be removed so that the system is self-adjusting. The valves 8 and10 also serve an important function when starting up the hydraulicsystem since the valves will then serve as bleed valves and ensure thatthe system is completely filled with pressure fluid thus eliminating airor gas pockets.

The modified construction shown in FIG. 4 completely eliminates anymechanical transmission through the end of the cylinder 1. In thismodification the stem 22 is replaced by a magnetic coupling of which onepart 60 is connected to the end of the spindle shown as 2a which isjournaled in the end 38a of the cylinder by means of a pin 62. In thismodification the end 38a ismade of non-magnetic material such asstainless steel, aluminum or plastics such as nylon or plexiglass. Theother part 64 of the magnetic coupling is journaled on a small shaft 66which carries the pointer shown as 68. Rotary movements of the spindle2a are thus transmitted through the parts 60 and 64 of the magneticcoupling to the pointer 68,

In both forms of construction illustrated various modifica tions arepossible; for example, the guide rod 26 is not essential and rotation ofthe piston 3 may be prevented, for example, by the provision of splinesengaging complementary grooves in the cylinder wall. The translation ofthe axial movement of the piston 3 into rotary movement of the spindle 2is of substantial advantage in avoiding the need to extend areciprocating member through the end of the cylinder. An indicatingsystem in accordance with the invention can be arranged in several ways.It is generally desirable for the cylinder 4 to be remotely controlled,for example, when used in connection with valves on ships. With such aninstallation the gauge cylinder 1 is usually installed at the controlstation so that the position of the remote valve can be checked at anytime. In some cases, however, in order to avoid the need for long runsof piping for the gauge cylinder and the reading of the indicator maythen be transmitted to the control station by means of an electricallyoperated repeater.

What is claimed is:

l. A volumetric gauge cylinder for a position indicator comprising aclosed cylinder having connections for pressure fluid at its ends, anon-rotatable piston movable within said cylinder under the fluidpressure, a rotatable spindle extending along the length of saidcylinder having a helical external configuration cooperating with, andforming a sealed fit with a correspondingly shaped opening in saidpiston so that linear movement of said piston is translated into rotarymovement of said spindle, an external indicator rotating in accordancewith the movement of said spindle, said piston including a pair ofoppositely connected, spring-loaded pressure relief valves which remainclosed during normal operation but open to permit the flow of pressurefluid if the pressure exceeds a predetermined value when said pistonreaches either end of its stroke, a hollow guide rod for said pistonhaving a sealing fit with an opening in said piston extending betweenthe two ends of said cylinder at one of which its interior communicateswith an external connection for pressure fluid and at the other of whichits interior communicates with the interior of said cylinder to form thepressure fluid connection at that end.

1. A volumetric gauge cylinder for a position indicator comprising aclosed cylinder having connections for pressure fluid at its ends, anon-rotatable piston movable within said cylinder under the fluidpressure, a rotatable spindle extending along the length of saidcylinder having a helical external configuration cooperating with, andforming a sealed fit with a correspondingly shaped opening in saidpiston so that linear movement of said piston is translated into rotarymovement of said spindle, an external indicator rotating in accordancewith the movement of said spindle, said piston including a pair ofoppositely connected, spring-loaded pressure relief valves which remainclosed during normal operation but open to permit the flow of pressurefluid if the pressure exceeds a predetermined value when said pistonreaches either end of its stroke, a hollow guide rod for said pistonhaving a sealing fit with an opening in said piston extending betweenthe two ends of said cylinder at one of which its interior communicateswith an external connection for pressure fluid and at the other of whichits interior communicates with the interior of said cylinder to form thepressure fluid connection at that end.